SQL-DATABASE ERROR

Database error in WoltLab Burning Board (): Link-ID == false, connect failed
mysql error: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)
mysql error number: 2002
mysql version: unknown
php version: 5.6.40
Date: 27.10.2021 @ 10:51
Script: /forgotpw.php?sid=bd1952b4b9a27b7cc12f8b86c497517c
Referer: